Multicast Radio Bearer Handover Sequence Number Buffering
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Solution Overview
Problem
In cellular communication networks, especially in LTE and 5G, handovers of user equipment (UE) involved in multicast and broadcast services often result in connectivity issues due to mismatches in Quality of Service (QoS) flows and radio bearers, leading to data duplication and loss during handover processes.
Innovation Solution
An apparatus and method that buffer packets and identify the highest protocol entity sequence number for seamless handover, using a second multicast and broadcast service radio bearer to configure user equipment for point-to-multipoint communication, ensuring continuous and lossless data transmission across base stations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If handover is performed for UE involved in multicast and broadcast services, then mobility is enabled, but data duplication and loss occur due to QoS flow and radio bearer mismatches
Solution Approach 1:
The target base station performs preliminary actions by buffering packets and identifying the highest protocol entity sequence number before the handover is completed. This allows the target base station to be prepared with the correct data state when the UE switches, preventing data loss and duplication during the transition.
Solution Approach 2:
The patent introduces an intermediary mechanism where the target base station acts as a mediator between the source base station and the UE during handover. It receives sequence number information from the source, buffers packets, and coordinates the data transmission to ensure seamless transition without duplication or loss.
2Speed
If traditional handover procedures are used, then handover speed is maintained, but connectivity issues arise due to QoS flow and radio bearer mismatches
Solution Approach 1:
The target base station performs preliminary configuration and packet buffering before the handover is finalized. This preliminary action ensures that when the handover executes quickly, the connectivity is already established and configured correctly, avoiding the mismatches that normally occur in traditional procedures.
3Productivity
If multiple QoS flows are mapped to a single radio bearer, then resource efficiency is improved, but complexity increases in managing handovers and sequence numbers
Solution Approach 1:
The patent changes the approach to handling multiple QoS flows by introducing a unified protocol entity sequence number that applies across all flows mapped to the same radio bearer. This parameter change simplifies the handover management complexity while maintaining the resource efficiency benefits of mapping multiple flows to a single bearer.
Data Source
AI summary
A method comprises receiving a handover request from a source BS, the handover request comprising a request for a handover of a UE involved in at least two QoS flows using a first MRB with the source BS, wherein the apparatus is using at least a second MRB for other UEs; starting to buffer packets for the UE; receiving a subsequent message comprising, for each of the at least two QoS flows, a CN SN of a first packet not transmitted by the source BS for that QoS flow; identifying a second packet with the highest protocol entity SN according to a protocol entity transmission order of the second MRB among packets which the source BS has delivered to the UE using the first MRB and the apparatus has transmitted to the other UEs using the second MRB; and transmitting a message configuring the UE to use the second MRB.